U.S. patent number 5,978,678 [Application Number 08/696,468] was granted by the patent office on 1999-11-02 for cellular telephone network routing method and apparatus for internationally roaming mobile stations.
This patent grant is currently assigned to Telefonaktiebolaget L M Ericsson (publ). Invention is credited to Michel Houde, Binh Nguyen.
United States Patent |
5,978,678 |
Houde , et al. |
November 2, 1999 |
Cellular telephone network routing method and apparatus for
internationally roaming mobile stations
Abstract
The registration notification signal sent to the home cellular
system when an internationally roaming cellular mobile station
registers in a foreign cellular system includes an identification
of the currently serving switching node. Upon subsequent receipt of
an incoming call dialed to the roaming mobile station home
directory number, the home cellular system signals the serving
cellular system and a temporary local directory number is assigned
and returned to the home cellular system. The switching node
identification is then processed to identify the proper
international dialing digits for calling the country where the
serving switching node is located. The returned temporary local
directory number is then appended to the identified international
dialing digits to form an international telephone number which is
used by the home cellular system to route the received call to the
currently serving cellular system for delivery to the called
internationally roaming mobile station.
Inventors: |
Houde; Michel (St-Laurent,
CA), Nguyen; Binh (St-Laurent, CA) |
Assignee: |
Telefonaktiebolaget L M Ericsson
(publ) (Stockholm, SE)
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Family
ID: |
26692191 |
Appl.
No.: |
08/696,468 |
Filed: |
August 14, 1996 |
Current U.S.
Class: |
455/433;
455/445 |
Current CPC
Class: |
H04W
8/12 (20130101); H04W 8/06 (20130101) |
Current International
Class: |
H04Q
7/38 (20060101); H04Q 007/20 () |
Field of
Search: |
;455/432,433,435,461,522,445,422 ;379/220 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0675663 |
|
0000 |
|
EP |
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WO 96/20574 |
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Jul 1996 |
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WO |
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Other References
The Mobile Communications Handbook, Jerry D. Gibson; CRC Press in
cooperation with IEEE Press; pp. 294-299, 1996. .
Yu, "Overview of EIA/TIA IS-41", IEEE International Symposium on
Personal, Indoor and Mobile Radio Communications, Boston, Oct.
1992, pp. 220-224. .
PCT International Search Report, Dec. 8, 1997, File No. PCT SE
97/00943..
|
Primary Examiner: Bost; Dwayne D.
Assistant Examiner: Legree; Tracy M.
Attorney, Agent or Firm: Jenkens & Gilchrist
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATION
This application for patent claims priority from previously filed
and co-pending U.S. Provisional Application for Pat. Ser. No.
60/019,410, entitled "CELLULAR TELEPHONE NETWORK ROUTING METHOD AND
APPARATUS FOR INTERNATIONAL ROAMING MOBILE STATIONS" and filed on
Jun. 7, 1996.
Claims
What is claimed is:
1. A method for delivering a call to an internationally roaming
mobile station, comprising the steps of:
storing in connection with a prior registration of the
internationally roaming mobile station an identification of a
switching node in a visited cellular system that is currently
serving the internationally roaming mobile station, the
identification being stored in a home location register for the
internationally roaming mobile station in a home cellular
system;
responsive to home cellular system receipt of an incoming call
dialed to a home directory number for the internationally roaming
mobile station, processing the home location register stored
switching node identification by the home cellular system to
identify the currently serving switching node location;
transmitting a routing request signal from the home cellular system
through an international gateway to the identified currently
serving switching node in the visited cellular system;
responsive to the currently serving switching node's receipt of the
routing request signal, assigning a temporary local directory
number to the internationally roaming mobile station;
transmitting the assigned temporary local directory number from the
visited cellular system back through the international gateway to
the home location register of the home cellular system;
processing of the stored switching node identification in the home
location register of the home cellular system to identify
international dialing digits for calling the country where the
currently serving switching node is located;
appending the received temporary local directory number to the
identified international dialing digits to form an international
telephone number; and
using the international telephone number to route the incoming call
from the home cellular system through the international gateway to
the currently serving switching node in the visited cellular system
for delivery to the called internationally roaming mobile
station.
2. The method as in claim 1 further including the step of storing
for the internationally roaming mobile station an identification of
a called party preferred long distance carrier.
3. The method as in claim 2 where the step of using further
includes the step of routing the incoming call through a particular
international gateway using the identified called party preferred
long distance carrier.
4. The method as in claim 3 further including the step of
translating the identified preferred long distance carrier and
wherein the step of routing further includes the step of routing
the incoming call through to the currently serving switching node
using the translated preferred long distance carrier.
5. The method as in claim 6 wherein the switching node
identification comprises a mobile switching center identifier.
6. The method as in claim 1 wherein the international dialing
digits comprise:
international access dialing digits; and
country code for the country within which the currently serving
switching node is located.
7. The method as in claim 6 wherein the international dialing
digits further comprise a carrier code for a long distance carrier
preferred for use in calling the internationally roaming mobile
station.
8. The method as in claim 7 wherein the step of using further
includes the step of routing the incoming call through a particular
international gateway using the long distance carrier identified by
the carrier code portion of the international dialing digits.
9. The method as in claim 8 further including the step of
translating the identified preferred long distance carrier and
wherein the step of routing further includes the step of routing
the incoming call through to the currently serving switching node
using the translated preferred long distance carrier.
10. The method as in claim 6 wherein the international dialing
digits further comprise a city code for the city within which the
currently serving switching node is located.
11. A home location register supporting delivery of incoming calls
to assigned mobile stations currently engaged in international
roaming, comprising:
means for storing an identification of a switching node currently
serving each internationally roaming mobile station assigned to the
home location register;
means responsive to an incoming call dialed to a home directory
number of a certain internationally roaming mobile station for
transmitting an international routing request to the currently
serving switching node; and
means responsive to receipt of a temporary local directory number
assigned by the currently serving switching node to that certain
internationally roaming mobile station for:
processing the stored identification of the currently serving
switching node to identify international dialing digits for calling
the country where the currently serving switching node is located;
and
appending the received temporary local directory number to the
identified international dialing digits to form an international
telephone number useful in internationally routing the incoming
call to the currently serving switching node.
12. The method as in claim 11 wherein the international dialing
digits comprise:
international access dialing digits; and
a country code for the country within which the currently serving
switching node is located.
13. The home location register as in claim 12 wherein the
international dialing digits further comprise a carrier code for a
long distance carrier preferred for use in calling the certain
internationally roaming mobile station.
14. The method as in claim 12 wherein the international dialing
digits further comprise a city code for the city within which the
currently serving switching node is located.
15. The home location register as in claim 11 wherein the switching
node identification comprises a mobile switching center identifier.
Description
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates to cellular telephone networks and,
in particular, to the routing of telephone calls to and from mobile
stations engaged in international roaming.
2. Description of Related Art
The mobility benefits provided to subscribers by cellular telephone
networks comprise, perhaps, their most important and effective
marketing advantage over and technical distinction with respect to
conventional wire line telephone service. It is common for
subscribers then to use their mobile stations not only in the
immediate geographic areas surrounding their homes and businesses,
but also to travel outside of their home cellular service area to
other cellular service areas. When this occurs, the subscribers and
their mobile stations are said to be "roaming".
Within one country, the plural cellular systems scattered
throughout that country are generally technically compatible with
each other. If the various service providers have billing and other
reciprocity service agreements with each other, a cellular
subscriber may then roam among and between those service areas and
still make and receive telephone calls. The process of registering
in the visited system occurs transparently to the subscriber. Even
absent an agreement with respect to billing, the overall system
technical compatibility allows the subscriber to arrange for a
personal billing agreement with the service provider, and thus
access the visited cellular system to make and receive telephone
calls. With respect to the reception of calls, the subscriber
mobile station is reached by dialing its originally (permanently)
assigned directory number.
The number of people owning cellular mobile stations has
dramatically increased in recent years. Furthermore, an increasing
number of geographic locations now have access to a cellular
telephone service. With this increase in numbers of users and
service availability, there also exists an increasing number of
instances where subscribers have the capability, and the desire to
engage in, of cellular roaming. In fact, it is now common for
persons to take their cellular mobile stations with them on
business trips and vacations. Often times these trips and vacations
involve travel to a different country.
While technical compatibility with the cellular system in the
visited country may be present, it is unlikely that the service
provider in the visited system and the subscriber's home service
provider have agreed to service provision and billing arrangements
with respect to internationally roaming subscribers. The subscriber
must accordingly contact the service provider in the visited
country and manually register their mobile station for service.
Once registered, the subscriber may then make a cellular telephone
call. Receiving a cellular telephone call, however, further
requires the assignment by the service provider of a temporary
directory number to the subscriber's mobile station. A party
desiring to call the subscriber may then have to use the assigned
temporary directory number rather than the subscriber's home
directory number in placing an international call to the
subscriber. Accordingly, to be accessible for incoming calls while
engaging in international roaming, the subscriber must inform
others of the newly assigned temporary number. Inconveniently, this
number is valid only for the currently visited cellular system. If
the subscriber should thereafter move to another country (or even
switch service providers within a single country), or perhaps
change to a different switch of the same service provider in the
same country, another manual registration must be made and another
temporary directory number is assigned for subsequent use.
There is a need then for a more efficient method and system for
enabling subscribers to engage in international roaming.
Preferably, such a method and system would allow a subscriber to
maintain use of their home directory number.
SUMMARY OF THE INVENTION
When an internationally roaming cellular mobile station registers
with a switching node of a currently serving foreign cellular
system, a registration notification signal is sent from the serving
cellular system to the home location register in the home cellular
system. This registration notification signal includes an
identification of the currently serving switching node which is
stored for later use. From processing the transmitted switching
node identification number, the home location register recognizes
that the mobile station is currently engaged in international
roaming and can accordingly handle any subsequently received
incoming calls.
When a call is subsequently dialed to the home directory number of
that internationally roaming mobile station, the home cellular
system processes the previously received switching node
identification information and signals the currently serving
cellular system with a routing request signal. Responsive thereto,
the serving cellular system assigns a temporary local directory
number to the roaming mobile station, and returns that number
information to the home location register in the home cellular
system. The home location register then processes the previously
stored switching node identification to identify the proper
international dialing digits (including the international access
digits, country code and city code, if necessary) for calling the
country where the serving switching node is located. The returned
temporary local directory number is then appended to the identified
international dialing digits to form an international telephone
number. The identified international dialing digits may further
include the carrier code for the long distance carrier preferred by
the subscriber owning the internationally roaming mobile station to
handle its long distance calling service. The formed international
telephone number is then used by the home cellular system to route
the received call to the currently serving cellular system for
delivery to the called internationally roaming mobile station.
BRIEF DESCRIPTION OF THE DRAWINGS
A more complete understanding of the method and apparatus of the
present invention may be acquired by reference to the following
Detailed Description when taken in conjunction with the
accompanying Drawings wherein:
FIG. 1 is a block diagram of an international cellular telephone
network;
FIG. 2 is a signal flow and network operation diagram illustrating
operation of the network of FIG. 1 in connection with the
registration of an internationally roaming mobile station; and
FIG. 3 is a signal flow and network operation diagram illustrating
operation of the network of FIG. 1 in connection with the delivery
of a call to the internationally roaming mobile station.
DETAILED DESCRIPTION OF THE DRAWINGS
Reference is now made to FIG. 1 wherein there is shown a block
diagram of an international cellular telephone network 10.
A first country cellular network 12 portion of the international
network 10 includes a plurality of interconnected switching nodes
(SN) 14. Although only three switching nodes 14 are shown, it will
be understood that the first country cellular network 12 likely
includes many more interconnected nodes. The switching nodes 14 may
comprise any one of a number of known telecommunications switching
devices, including those commonly used and known in the art for
providing either digital or analog cellular telephone service to a
plurality of subscriber mobile stations 16. The switching nodes 14
are interconnected for communication via both signaling links 18
(illustrated with solid lines) and voice trunks 20 (illustrated
with broken lines). The voice trunks 20 provide voice and data
communications paths used to carry subscriber communications
between the nodes 14. The signaling links 18 carry command signals
between the nodes 14 used for setting up and tearing down voice and
data communications links over the voice trunks 20, and for
controlling the provision of service features to the subscriber
mobile stations 16. The switching nodes 14 are connected to a home
location register (HLR) data base 22 by means of signaling links
24. The home location register data base 22 stores information
concerning the assigned subscriber mobile stations 16 comprising
location information and service information. Each switching node
14 is further connected to a visitor location register (VLR) data
base 26 (shown integrated with the switching node as an MSC/VLR)
for temporary storage of subscriber information with respect to
those subscriber mobile stations 16 currently being served by that
switching node.
A second country cellular network 32 portion of the international
network 10 includes a plurality of interconnected switching nodes
(SN) 34. Although only three switching nodes 34 are shown, it will
be understood that the second country cellular network 32 likely
includes many more interconnected nodes. The switching nodes 34 may
comprise any one of a number of known telecommunications switching
devices, including those commonly used and known in the art for
providing either digital or analog cellular telephone service to a
plurality of subscriber mobile stations 36. The switching nodes 34
are interconnected for communication via both signaling links 38
(illustrated with solid lines) and voice trunks 40 (illustrated
with broken lines). The voice trunks 40 provide voice and data
communications paths used to carry subscriber communications
between the nodes 34. The signaling links 38 carry command signals
between the nodes 34 used for setting up and tearing down voice and
data communications links over the voice trunks 40, and for
controlling the provision of service features to the subscriber
mobile stations 36. The switching nodes 34 are connected to a home
location register (HLR) data base 42 by means of signaling links
44. The home location register 42 stores information concerning the
assigned subscriber mobile stations 36 comprising location
information and service information. Each switching node 34 is
further connected to a visitor location register (VLR) data base 46
(shown integrated with the switching node as an MSC/VLR) for
temporary storage of subscriber information with respect to those
subscriber mobile stations 36 currently being served by that
switching node.
An international gateway (IGW) 50 is used to connect at least one
of the switching nodes 14 of the first country cellular network 12
with at least one of the switching nodes 34 of the second country
cellular network 32. The connections involved include a signaling
link 18 and voice trunks 20 between the switching node 14 of the
first country cellular network 12 and the international gateway 50.
Similar signaling link 38 and voice trunk 40 connections are
provided between the switching node 34 of the second country
cellular network 32 and the international gateway 50.
Instances may occur where a first country cellular network 12
subscriber travels to the second country and wishes to use his or
her mobile station 16(1) in the second country cellular network 32.
Historically, this required the subscriber to manually register in
the second country cellular network 32. Manual registration
establishes the billing arrangement for the subscriber to pay for
use of and access to the second country cellular network 32, and
also assigns to the mobile station 16 a temporary directory number.
This assigned temporary directory number, rather than the home
directory number for the mobile station 16, may then have to be
dialed by a party in either the first or second country when they
want to call that internationally roaming subscriber. It would be
preferred, however, if contact could be made with the subscriber
instead by dialing the home directory number.
Reference is now additionally made to FIG. 2 wherein there is shown
a signal flow and network operation diagram illustrating operation
of the network 10 of FIG. 1 in connection with the registration of
an internationally roaming mobile station 16(1). The
internationally roaming mobile station 16(1) sends a registration
signal 100 to its selected serving switching node 34 in the second
country cellular network 32. This registration signal includes an
identifier of the mobile station 16(1) comprising, for example, its
mobile identification number (MIN), electronic serial number (ESN),
international mobile station identifier (IMSI), and/or its
temporary mobile station identifier (TMSI). The serving switching
node 34 processes (action 102) the mobile station identifier to
identify the home location register 22 in the first country
cellular network 12 to which that internationally roaming mobile
station 16(1) belongs (i.e, is assigned). The serving switching
node 34 then sends a registration notification signal 104 (over the
signaling links 38, through the international gateway 50, and over
the signaling links 18 and 24) for delivery to the home location
register 22. This registration notification signal 104 may comprise
an IS-41 REGNOT signal or other equivalent standardized or
proprietary message, and includes an identification number (i.e.,
MSCID) for the serving switching node (mobile switching center).
The home location register 22 then stores (action 106) the
switching node identification number for the currently serving
switching node 34 in the subscriber profile for the internationally
roaming mobile station 16(1). The data base of the home location
register 22 includes information identifying that the switching
node identification number is assigned to a switching node 34
located in the second country cellular network 32, and that its
subscriber is currently engaged in international roaming.
Responsive to receipt of the registration notification signal 104,
a service profile 108 for the registering mobile station 16(1) is
returned from the home location register 22 to the serving
switching node 34 (for storage in its associated visitor location
register). Once registered, the mobile station 16(1) may originate
calls 110 to cellular or wire line subscribers either within the
current country, or to other countries.
Reference is now additionally made to FIG. 3 wherein there is shown
a signal flow and network operation diagram illustrating operation
of the network 10 of FIG. 1 in connection with the delivery of a
call to the internationally roaming mobile station 16(1). A call
200 dialed to the home directory number of the internationally
roaming mobile station 16(1) originates from another cellular
subscriber or the public switched telephone network (PSTN) and is
received at one of the switching nodes 14 (i.e., gateway node) of
the first country cellular network 12. It will be noted that the
number dialed comprises the originally assigned home directory
number. Using the signaling link 24, the switching node 14
interrogates the home location register 22 with a location request
signal 202 including the dialed home directory number. This
location request signal 202 may comprise an IS-41 LOCREQ signal or
other equivalent standardized or proprietary message. The home
location register 22 processes (action 204) the location request
signal, in view of the previously received registration
notification signal 104, to determine the location (i.e., serving
switching node 34 within the second country cellular network 32) of
the called mobile station 16(1). The home location register 22 then
signals the serving switching node 34 for the called mobile station
16(1) (over signaling links 18 and 24, through international
gateway 50, and over signaling link 40) with a routing request
signal 206 to route the call. This routing request signal may
comprise an IS-41 ROUTEREQ signal or other equivalent standardized
or proprietary message. Responsive to the signal 206, the serving
switching node 34 assigns (action 208) a temporary local directory
number (TLDN) to the international roaming mobile station 16(1),
and sends a routing request return result signal 210 including the
assigned temporary local directory number to the home location
register 22 via the international gateway 50. From processing of
the previously stored switching node identification for switching
node 34, the home location register identifies the country where
that node (34) is located and retrieves (action 212) its country
code (CC) designation. The country code and returned temporary
local directory number are then appended to the proper
international dialing access digits (IDAD) to form (action 214) the
international number for contacting the called international
roaming mobile station 16(1). It will be noted that if the returned
temporary local directory number does not include a city code, this
may also be determined from processing the switching node
identification number and then appended by action 214 at the proper
location to complete the international number. It will further be
noted that the subscriber owning the international roaming mobile
station 16(1) may further have a long distance carrier preference,
and in such instances the carrier code for that preferred carrier
is also appended by action 214 at the proper location to complete
the international number. The home location register 22 then sends
a location request return result signal 216 including the formed
international number to the gateway switching node 14. The gateway
switching node 14 uses the formed international number to deliver
(through connects) 218 the incoming call 200 over the voice trunks
20 and 40, and through the international gateway 50, to the serving
switching node 34. The call delivery is routed to the international
gateway 50 in accordance with the designated carrier code. Using
the link between the temporary local directory number and the
mobile identification number/electronic serial number of the
internationally roaming mobile station 16(1), the switching node 34
signals the mobile station, establishes a call connection 220 and
completes call delivery. Furthermore, the included carrier code may
be translated (action 222) by the international gateway 50 to
designate a particular long distance carrier for use in routing the
call from the international gateway to the switching node 34.
The foregoing may be better understood through reference to the
following example. Assume that the first country is Canada, and the
second country is France. When the internationally roaming mobile
station 16(1) registers in the French cellular network 32, its
mobile station identifier is processed to identify that the mobile
station belongs (i.e., is assigned) to home location register 22 in
the Canadian cellular network 12. The identification number for the
serving switching node 34 is sent to the home location register 22
for storage in the roaming mobile station's service information.
The service profile for the roaming mobile station 16(1) is also
returned to the serving switching node 34.
Now assume that a call is received at a gateway switching node 14
of the Canadian cellular network 12 dialed to the home directory
number of mobile station 16(1). The home location register 22 is
interrogated with the location request signal 202, which is
processed to determine mobile station location associated with
serving switching node 34 in the French cellular network 32. A
routing request signal 206 is then sent by the home location
register 22 to the serving switching node 34 to route the call.
Responsive thereto, the home location register 22 is informed of
the temporary local directory number which has been assigned to the
internationally roaming mobile station 16(1). The previously stored
switching node identification is then processed to identify the
country of France and the French country code (CC=33) designation.
The country code and returned temporary local directory number are
then appended to the proper international dialing access digits
(IDAD=011) to form the international number (011-33-TLDN) for
contacting the called internationally roaming mobile station 16(1).
In instances where the returned temporary local directory number
does not include the city code, the stored switching node
identification is then further processed to identify the city code
(City) in France for the switching node 34, and that code is added
to the formed international number (011-33-City-TLDN). Furthermore,
where the subscriber owning the mobile station 16(1) has specified
a particular long distance carrier, the carrier code (Carrier) for
that carrier is retrieved from the home location register 22 and
added to the formed international number (011-Carrier-33-TLDN).
Using the formed international number, the gateway switching node
14 delivers (through connects) the incoming call to the serving
switching node 34 for delivery to the internationally roaming
mobile station 16(1). This through connection recognizes the
designated carrier code for call routing to the international
gateway 50, and a translation of that code for call routing to the
serving switching node 34.
Although preferred embodiments of the present invention have been
illustrated in the accompanying Drawings and described in the
foregoing Detailed Description, it will be understood that the
invention is not limited to the embodiments disclosed, but is
capable of numerous rearrangements, modifications and substitutions
without departing from the spirit of the invention as set forth and
defined by the following claims.
* * * * *